Frequency reducer



April 8, 1947. H. M. HUGE 2,418,642

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Patented Apr. 8, 1947 FREQUENCY REDUCED Henry Martin Huge, Lorain, Ohio,assignor of one-half to Closman P. Stocker and one-half to E. M. HeavensApplication June 5, 1944, Serial No. 538,839

This invention relates to frequency changers, and in particular, to afrequency changing transformer capable of generating 'subharmonics ofthe input frequency. The subject matter of this application is anextension of the invention shown and described in my application SerialNo. 505,611 I filed October 9, 1943.

It is an object of this invention to generate subharmonics of the inputfrequency in a static frequency changer.

Another object of this invention is to provide an improved method forautomatically starting subharmonic oscillations by means of a relay.

Still another object of this invention is to produce a frequencychanging transformer for the generation of subharmonics.

Other objects and a better understanding of my invention may be had byreferring to the following specifications and claims, together with theaccompanying drawings:

Figure 1 shows diagrammatically a subharmonic generator made accordingto my invention with a three-legged saturable magnetic core having theprimary winding on the central core member,

Figure 2 shows a different winding arrangement on the three-legged coreand also shows my improved method of starting subharmonic oscillations,

Figure 3 is a modification of the arrangement of Figure 2 provided withtwo windings for operation on two difierent input voltages, and

Figure 4 is another modification of the arrangement of Figure 2 showingadifferent output arrangement.

with more particular reference to Figure 1, there is shown a magneticcore structure having three core members i5, i6 and I1. Primary winding31 on the central core member i5 is energized from the alternatingcurrent source iii. The secondary windings 38 and 39 on the two outercore members i6 and ii are connected in series with each other andconnected to capacitor H in series with relay winding I9. The secondarywindings 38 and 39 are polarized oppositely with respect to the primarywinding 31, so that the total voltage from source it) which is appliedto capacitor i4 is the difference between the voltages in windings 38and 39. Relay contacts 20 short-circuit secondary winding 38 when therelay winding is is not energized. Under this condition, the flux of thesource frequency through the central core member I5 is forced throughcore member I! for its return path, inducing a voltage in winding 39which is applied to capacitor it. The charging 1 Claims. (c1. 172-281)current of capacitor i4 flowing through relay winding [3 opens the relaycontacts 20 and inserts secondary winding 38 in the circuit. The chargeon capacitor ll at the moment the relay contacts open then flows awaythrough the secondary windings 38 and 39, magnetizing the core andstarting the subharmonic oscillations in the secondary circuit. Thesubharmonic current through capacitor II and relay winding i9 holds openthe relay contacts 20 as long as the oscillations continue, but shouldthey stop, the relay recioses contacts 20 and restarts the oscillations.

In normal operation, the flux through the central core member i5 ispredominantly of the frequency of source i0, because the primary winding31 is connected directly to source iii. The

subharmonic flux flows around through core,

members l6 and i1 and in these members is superimposed on the flux ofthe source frequency. The superimposed fluxes saturate the core andtheir interaction converts power from the source frequency to thesubharmonic frequency to sustain the subharmonic oscillations. I' preferto make windings 38 and 39 with somewhat different numbers of turns whencore members It and ii are magnetically equal. This provides couplingbetween the primary winding 31 and the secondary windings. Under lowflux density, the coupling between primary and secondary is weak but itincreases with increasing flux density. The effect of the windingarrangement shown, therefore, is to provide a saturable leakagereactance between the primary and secondary circuits. The variations insaturation produced by the subharmonic oscillations initiated by theaction of the relay contacts 20 act to maintain the subharmonicoscillations.

The output windings 43 and 44 on the core members i6 and il areconnected in series with each other and preferably polarized to add thesubharmonic voltages induced in them. By varying the relative numbers ofturns on these two windings, I am able to control the harmonic contentof the voltage supplied to the load connected to the output terminals 4|and 42. For some load requirements the harmonic content of the voltageappearing across either one of the windings 43 or 44 may be suitable forsupplying to the load. In this case the load may be connected acrossoutput terminals All and 4i or 40 and 42, eliminating the necessity fortwo output windings connected in series.

The winding arrangement shown in Figure 2 might be considered asapproximately the reverse of that shown in Figure 1. In Figure 2 theprimary windings I2 and I! are connected in series and wound on the twoouter core members II and I1. With core members l3 and i1 magneticallyequal, windings l2 and I! may be made with substantially the sam numberof turns to provide cancelling fluxes through the central core memberIS. The secondary winding ii, on core member i5, is connected to thecapacitor H in series with relay winding l9 and is also connected inseries with the primary windings to provide the necessary couplingbetween the primary and secondary circuits.

When the voltage from source i is first applied, the normally closedrelay contacts 20 connect the winding ll directly to the source III. Thecurrent from source In flowing through capacitor I4 and relay winding l8operates the relay and opens contacts 20. The charge on capacitor IIwhen the relay contacts open flows oil through winding H on core member15, magnetizing the core and starting the subharmonic oscillationsthrough winding II and capacitor M. In operation, the flux through coremember I5 is largely subharmonlc flux. This is true because the lowimpedance of capacitor H at the frequency of source l0 tends toshort-circuit the winding H at the frequency of source Hi. Thesubharmonic flux through core member l5 divides between the outer coremembers I6 and I! which act as its return path. Since these outer coremembers are magnetized by source iii, the subharmonic flux in them issuperimposed on the fundamental frequency flux produced by source [0.The superposition of the fluxes in these core members, which becomesaturated by the combined magnetization, produces a power transfer i'roi" the fundamental to the subharmonic frequ .ncy and sustains thesubharmonic oscillation in the circuit of capacitor H and secondarywinding H. The subharmonic voltage is supplied to a load by means of theoutput winding ll on core member IS. The output-frequency most easilyproduced is one-third the input frequency, but other subharmonics canalso be produced when the elements are suitably proportioned.

The unbalanced magnetization of the outer core members l8 and I!produced by the secondary winding ll connected in series with themprovides coupling between the centrally located core member l5, whichcarries secondary winding II, and the outer core members l6 and I! whichcarry the primary windings l2 and IS. The coupling thus provided betweenprimary and secondary is not a tight coupling, but has an eilectivesaturable leakage reactance between the primary and secondary circuits.It is also possible to provide the required coupling without connectingthe secondary winding II in series with the primary windings by makingprimary windings l2 and I3 unequal or otherwise unbalancing thestructure.

The method of starting the oscillations shown in Figure 2, constitutesan improvement over the method shown in Figure l. I have found thatimproved starting action can be obtained with this method because thecapacitor I4 is connected directly to'the energizing source during thestarting interval and the effects of leakage reactance between thesource and the capacitor which may occur with the arrangement of Figure1 are substantially eliminated.

Figure 3 is the schematic diagram of the preferred embodiment of myinvention, provided with double windings on the outer core members IIand I! and provided with a step-up winding for supplying increasedvoltage to capacitor ll. Primary windings II and I: on core member I! inFigure 3 take the place of primary winding I! in Figure 2 and primarywindings 23 and 24 on core member I! in Figure 3 take the place ofprimary winding is in Figure 2.

The secondary winding I I is provided with tape 26 and 2'! so that onlya portion of the secondary winding l l is connected in series with theprimary windings in the energizing circuit. The primary windings inFigure 3 are shown connected in parallel, and connected to tap 2'! onwinding II, for operation on a low input voltage, but these windings maybe connected in series with each other in which case I prefer to connectthem to tap 28 instead of tap 21 to provide for operation on an inputvoltage twice as great.

Secondary winding II is connected to capacito H and relay winding '9 asin Figure 2. However, Figure 3 shows an arrangement for introducing highorder harmonics in the voltage supplied to the load. These harmonic areprovided by the saturable inductance having windings 28 and 18. Thewinding 28 is connected in series with capacitor H and is shunted by acapacitor II which serves to accentuate the desired harmonics in theoutput voltage. Winding 29 of the saturable inductance is connected inseries with the output winding I 8 to supply the high order harmonics tothe load. These harmonics are frequently required when the converter isused to supply telephone ringing current, in which case the audiblecomponents of the output voltage serve as an audible ringing tone.

The arrangement shown in Figure 3 makes it possible to supply increasedvoltage to the capacitor ll so that a small high-voltage capacitor of aneconomical size can be used. One end of secondary winding II isconnected directly to the source IO and to capacitor I4 in Figure 3. Therelay contacts 20 connect the opposite side of source III to a tap II onsecondary winding ll during the starting interval. In this way thevoltage 01' source I0 is stepped up and fed to the capacitor to providethe initial charge for starting the subharmonic oscillations.

The tap II is provided so when the converter is operated on the higherinput voltage with the primary windings in series, the voltage suppliedto the capacitor ll during the starting interval can be madesubstantially the same as when operated on the lower input voltage. Asexplained in connection with Figure 2, this method of energizing thecapacitor has the advantage of providing a relatively direct coupling tothe energizing source and minimizes any possibility of leakage reactanceeffects during the starting interval.

The operation of the circuit of Figure 3 is substantially the same asthe operation of the circuit of Figure 2. The charging current ofcapacitor I through relay winding I! opem the relay contacts 20 andcauses the discharge current of capacitor ll to initiate the subharmonicoscillations. Capacitor 25 in Figure 3 is connected in series with theload to prevent possible overloads on the converter from stopping thesubharmonic oscillations.

Figure 4 shows a modified output winding arrangement which may beapplied also to the circuits shown in Figures 2 and 3 or which may becombined with the arrangements shown in Figures 2 and 3 to produce thedesired results. Figare 4 differs from Figure 3 only in its outputwinding arrangement and in that it has single windings. and is notarranged for operation on two different input voltages as is Figure 3.The secondary windings 33 and 34 in Figure 4 on the two outer coremembers i6 and i! are preferably phased to add the subharmonic voltagesinduced in them, They may be proportioned in any desired manner toprovide varying harmonic content in the voltage supplied to the load; orin some cases, it may be possible to use the output winding arrangementmentioned in connection with Figure 1, in which only one output windingon one of the outer core members is used.

In operating characteristics, the circuit shown in Figure 4 issubstantially the same as that shown in Figure 3. The secondary windingII is provided with a tap 35 connected to the relay contacts 20 to stepup the starting voltage to capacitor id. The primary windings i2 and I3are connected in series with each other and with a portion of secondarywinding II as provided by the tap 2! on winding ii. The flux through thecentral core member I5 is predominantly subharmonic flux and it dividesunequally between the two outer core members i6 and IT in its returnpath.

The arrangements shown for varying the harmonic content of the loadvoltage are merely examples of many circuit modifications which might beapplied to this end. For example, the harmonic content of the outputvoltage supplied from the secondary winding I8 in Figure 3 may be variedwhen it is required, by supplying the capacitor H with voltage both fromsecondary winding ii and from one of the primary windings. This modifiedconnection allows more or less flux of the frequency of source ID toflow through the central core member i5, depending upon the amount andpolarity of the primary voltage which is supplied to capacitor l4.

Although I have described my invention with a certain degree ofparticularity, it is to be understood that the present disclosure hasbeen made only by way of example, and that numerous changes in thedetails of construction and the combination and arrangement of parts maybe resorted to without departing from the spirit and scope of theinvention as hereinafter claimed.

I claim as my invention:

l. A frequency reducer comprising in combination a magnetic core havingfirst, second, and

third core members, the first and second core members havingsubstantially the same magnetic characteristics, first and secondsubstantially equal windings respectively on said first and second coremembers adapted to be energized from a source of alternating current andto produce opposing fluxes in the third core member, a third winding onthe third core member, a capacitor adapted to be energized from saidthird winding, at least a portion of the third winding being adapted tobe energized from the source in series with the first winding, andstarting means adapted to connect said third winding to said source ofalternating current to initiate oscillations of the reduced frequency inthe third winding,

2. A frequency reducer comprising in combination a magnetic core havingfirst, second, and third core members, first and second windingsrespectively on said first and second core members adapted to beenergized from a source of alternating current and to produce opposingfluxes in the third core member, a third winding on the .third coremember, a capacitor adapted to be energized from said third winding, atleast a portion of the third winding being adapted to be energized fromthe source in series with the first winding, and starting means adaptedto connect said third winding to said source of alternating current toinitiate oscillations of the reduced frequency in the third winding.

3. A frequency reducing arrangement comprising in combination a magneticcore having first, second, and third core members with first, second,and third windings respectively thereon, the first. second, and thirdwindings being connected in series and adapted to be energized by analternating current source, a capacitor adapted to be energized from thethird winding, is starting relay adapted to connect said third windingto said source to produce an initial charge on the capacitor to initiateoscillations of the reduced frequency through it, and an output circuitfor supplying the reduced frequency to a load.

4. A subharmonic generator adapted to be energized by a source ofalternating current and to supply a load with power at a subharmonicfrequency, comprising in combination a magnetic core having first,second, and third core members, windings on said first and second coremembers adapted to be energized by the source of alternating current, awinding on said third core member. a capacitor connected across saidwinding on the third core member, and a relay adapted to connect atleast a portion of said winding on the third core member across saidsource of alternating current to supply an initial charge to saidcapacitor to start subharmonlc oscillations through the capacitor.

5. A subharmonic generator comprising in combination magnetic core meanshaving at least three core members, primary winding means on the coremeans adapted to be energized by a source of alternating current,secondary winding means on the core means, capacitive means connectedacross the secondary winding means, and starting means comprising arelay adapted to connect said secondary winding means to the source ofalternating current to produce a starting transient in the secondarywinding means to initiate subharmonic oscillations therein. said primaryand secondary winding means being disposed on at least two of the coremembers and having effectively a saturable leakage reactance betweenthem.

6. A subharmonic generator comprising in combination, magnetic coremeans having at least three core members, primary winding means on thecore means adapted to be energized by a source of alternating current,secondary winding means on the core means, capacitive means energized bythe secondary winding means. starting means adapted to connect thesecondary winding means to the source to produce a starting transient toinitiate subharmonic oscillations through the capacitive means, andoutput winding means inductively related to the secondary winding means,said winding means being disposed on at least two of the core memberswith an effective saturable leakage reactance between the primary andsecondary winding means.

7. In a frequency reducer comprising saturable magnetic core meanshaving first, second, and third core members with first, second, andthird Winding means respectively thereon, with a capacitor energizedfrom the third winding means and with the first and second winding meansbeanew:

7 8 in: serially connected and adapted to produce 7 opposing fluxes inthe third core member when REFERENCE! CITED energized by an alternatingcurrent source. The mum rum m of m m m starting means for initiatingaubharmonic 05- m t clllations m the third winding means, said startingmeans comprising a. relay adapted to connect Um PAW the third windingmeans to the source to pro- Nu b N n. mg. duce an initial charge on thecflpa w 2,364,532 Huge Dec. 5, 19

HENRY MARTIN HUGE.

